JPWO2016017170A1 - DC-DC converter - Google Patents

Abstract

The subject of this invention is providing the DC-DC converter which can perform voltage conversion bidirectionally and can improve conversion efficiency. A DC-DC converter (10) according to the present invention includes a switching circuit (1), an inductor (L1), a capacitor (C1), a transformer (T1), a switching circuit (2), and a control circuit (3). A first winding (N11) is electrically connected between the pair of connection ends (1c, 1d) of the switching circuit (1). The series circuit (4) of the inductor (L1) and the capacitor (C1) is electrically connected in series with the first winding (N11) between the pair of connection ends (1c, 1d).

Description

  The present invention generally relates to a DC-DC converter, and more particularly to a DC-DC converter that performs bidirectional voltage conversion.

  Conventionally, a bidirectional DC-DC converter capable of transforming between a high-voltage first battery and a low-voltage second battery has been proposed (see Document 1 [Japanese Patent Publication No. 2009-177940]). ).

  A bidirectional DC-DC converter described in Document 1 (hereinafter, “DC-DC converter of Conventional Example 1”) includes a transformer, a primary side orthogonal transform unit, a secondary side orthogonal transform unit, a booster circuit, It has.

  Conventionally, a power conversion circuit that bidirectionally transforms between a first terminal and a second terminal has been proposed (see Document 2 [Japanese Published Patent Publication No. 2014-57387]).

  The power conversion circuit described in Document 2 (hereinafter, “DC-DC converter of Conventional Example 2”) includes a two-stage transformer circuit and a control circuit. The two-stage transformer circuit includes a chopper circuit and a bidirectional transformer circuit.

  In the DC-DC converter of Conventional Example 2, when the voltage is transformed from the first terminal to the second terminal, the operation is not performed by the chopper circuit, but the voltage is transformed using the transformer provided in the bidirectional transformer circuit. In the DC-DC converter of Conventional Example 2, when the voltage is transformed from the second terminal to the first terminal, the operation is performed by the chopper circuit, and the voltage is transformed by using the chopper circuit and the transformer.

  By the way, in the DC-DC converter of Conventional Example 1, in order to perform voltage conversion in both directions, a conversion circuit (transformer, primary side orthogonal transform unit and secondary side orthogonal transform unit) and a booster circuit are required. A two-stage circuit configuration is provided. Therefore, it is difficult to perform voltage conversion in both directions only with the conversion circuit in the DC-DC converter of Conventional Example 1. Moreover, since the DC-DC converter of Conventional Example 1 has a two-stage circuit configuration, it is difficult to improve the conversion efficiency.

  Further, in the DC-DC converter of the conventional example 2, since the operation by the chopper circuit is not performed at the time of the transformation from the first terminal to the second terminal, the unidirectional voltage is compared with the DC-DC converter of the conventional example 1. Conversion efficiency can be improved in conversion.

  However, in the DC-DC converter of Conventional Example 2, since the operation by the chopper circuit is performed during the transformation from the second terminal to the first terminal, it is difficult to improve the conversion efficiency in bidirectional voltage conversion. Moreover, since the DC-DC converter of Conventional Example 2 is also provided with a two-stage circuit configuration (chopper circuit and bidirectional transformer circuit), it is difficult to improve the conversion efficiency.

  An object of the present invention is to provide a DC-DC converter capable of performing voltage conversion in both directions and improving conversion efficiency in bidirectional voltage conversion.

  A DC-DC converter according to an aspect of the present invention is a DC-DC converter that performs bidirectional voltage conversion between a first DC voltage and a second DC voltage. The DC-DC converter includes a first switching circuit including a first switching element, an inductor, a capacitor, and a transformer. The DC-DC converter includes a second switching circuit including a second switching element, and a control circuit that controls the first switching circuit and the second switching circuit. The first switching circuit is configured to bidirectionally convert the first DC voltage and the first AC voltage. The second switching circuit is configured to bi-directionally convert the second AC voltage and the second DC voltage. The transformer includes a first winding and a second winding. The first winding and the second winding are magnetically coupled. The first winding is electrically connected between a pair of connection ends on the first AC voltage side in the first switching circuit. The second winding is electrically connected between a pair of connection ends on the second AC voltage side in the second switching circuit. The series circuit of the inductor and the capacitor is electrically connected in series with the first winding between the pair of connection ends in the first switching circuit.

It is a circuit diagram of the DC-DC converter of one embodiment. It is a timing chart when converting the 1st direct-current voltage into the 2nd direct-current voltage regarding the DC-DC converter of one embodiment. It is a timing chart when converting the 2nd direct-current voltage into the 1st direct-current voltage regarding the DC-DC converter of one embodiment. In the DC-DC converter of one embodiment, it is explanatory drawing explaining the operation mode of a control circuit. It is a timing chart when converting the 1st direct-current voltage into the 2nd direct-current voltage by the 1st operation mode about the DC-DC converter of one embodiment. It is a timing chart when converting the 2nd direct-current voltage into the 1st direct-current voltage by the 1st operation mode about the DC-DC converter of one embodiment. It is a timing chart when converting the 1st direct-current voltage into the 2nd direct-current voltage by the 2nd operation mode about the DC-DC converter of one embodiment. It is a timing chart when converting the 2nd direct-current voltage into the 1st direct-current voltage by the 2nd operation mode about the DC-DC converter of one embodiment.

  Below, the DC-DC converter 10 of one Embodiment is demonstrated, referring FIGS. 1-3.

  The DC-DC converter 10 is a DC-DC converter that bi-directionally converts the first DC voltage Vd1 and the second DC voltage Vd2.

  The DC-DC converter 10 includes a switching circuit 1, an inductor L 1, a capacitor C 1, a transformer T 1, a switching circuit 2, and a control circuit 3. The transformer T1 includes a first winding N11 and a second winding N12. The first winding N11 and the second winding N12 are magnetically coupled.

  In the DC-DC converter 10, the switching circuit 1 corresponds to a first switching circuit. In the DC-DC converter 10, the switching circuit 2 corresponds to a second switching circuit.

  The switching circuit 1 is configured to bi-directionally convert the first DC voltage Vd1 and the first AC voltage Va1. The switching circuit 1 is, for example, a full bridge circuit.

  The switching circuit 1 includes a pair of connection ends 1a and 1b, a pair of connection ends 1c and 1d, and four switching elements Q1 to Q4. The pair of connection ends 1a and 1b correspond to a pair of connection ends on the first DC voltage Vd1 side in the switching circuit 1. The pair of connection ends 1c and 1d correspond to a pair of connection ends on the first AC voltage Va1 side in the switching circuit 1. Each of the four switching elements Q1 to Q4 corresponds to a first switching element.

  For example, the storage battery 11 is electrically connected between the pair of connection ends 1a and 1b. Examples of the storage battery 11 include a lead storage battery and a lithium ion battery. The connection end 1 a is electrically connected to the plus terminal of the storage battery 11. The connection end 1 b is electrically connected to the negative terminal of the storage battery 11. The voltage between the terminals of the storage battery 11 is the first DC voltage Vd1.

  A series circuit of an inductor L1, a capacitor C1, and a first winding N11 is electrically connected between the pair of connection ends 1c and 1d. In short, the first winding N11 is electrically connected between the pair of connection ends 1c and 1d. The series circuit 4 of the inductor L1 and the capacitor C1 is electrically connected in series with the first winding N11 between the pair of connection ends 1c and 1d in the switching circuit 1. The series circuit 4 constitutes a series type resonance circuit.

  Each of the four switching elements Q1 to Q4 is a normally-off type n-channel MOSFET, for example. The diodes added to the four switching elements Q1 to Q4 in FIG. 1 are parasitic diodes.

  The drain terminal of the switching element Q1 is electrically connected to the connection end 1a. The source terminal of the switching element Q1 is electrically connected to the drain terminal of the switching element Q2. The gate terminal of the switching element Q1 is electrically connected to the control circuit 3.

  The drain terminal of the switching element Q2 is electrically connected to the connection end 1c. The source terminal of the switching element Q2 is electrically connected to the connection end 1b. The gate terminal of the switching element Q2 is electrically connected to the control circuit 3.

  The drain terminal of the switching element Q3 is electrically connected to the drain terminal of the switching element Q1. The source terminal of the switching element Q3 is electrically connected to the drain terminal of the switching element Q4. The gate terminal of the switching element Q3 is electrically connected to the control circuit 3.

  The drain terminal of the switching element Q4 is electrically connected to the connection end 1d. The source terminal of the switching element Q4 is electrically connected to the source terminal of the switching element Q2. The gate terminal of the switching element Q4 is electrically connected to the control circuit 3.

  The switching circuit 1 is not limited to a full bridge circuit, and may be a half bridge circuit or a push-pull circuit, for example.

  Similar to the switching circuit 1, the switching circuit 2 is configured to bi-directionally convert the second AC voltage Va2 and the second DC voltage Vd2. The switching circuit 2 is, for example, a full bridge circuit.

  The switching circuit 2 includes a pair of connection ends 2a and 2b, a pair of connection ends 2c and 2d, and four switching elements Q5 to Q8. The pair of connection ends 2a and 2b correspond to a pair of connection ends on the second AC voltage Va2 side in the switching circuit 2. The pair of connection ends 2c and 2d correspond to a pair of connection ends on the second DC voltage Vd2 side in the switching circuit 2. Each of the four switching elements Q5 to Q8 corresponds to a second switching element.

  The second winding N12 is electrically connected between the pair of connection ends 2a and 2b.

  For example, a DC voltage source 12 is electrically connected between the pair of connection ends 2c and 2d. The DC voltage source 12 is, for example, an electrolytic capacitor. The connection end 2c is electrically connected to a high potential side terminal of the electrolytic capacitor. The connection end 2d is electrically connected to a terminal on the low potential side of the electrolytic capacitor. The terminal voltage of the DC voltage source 12 is the second DC voltage Vd2. The DC voltage source 12 is an electrolytic capacitor, but is not limited to this.

  Each of the four switching elements Q5 to Q8 is, for example, a normally-off type n-channel MOSFET. The diodes added to the four switching elements Q5 to Q8 in FIG. 1 are parasitic diodes.

  The drain terminal of the switching element Q5 is electrically connected to the drain terminal of the switching element Q7. The source terminal of the switching element Q5 is electrically connected to the drain terminal of the switching element Q6. The gate terminal of the switching element Q5 is electrically connected to the control circuit 3.

  The drain terminal of the switching element Q6 is electrically connected to the connection end 2a. The source terminal of the switching element Q6 is electrically connected to the source terminal of the switching element Q8. The gate terminal of the switching element Q6 is electrically connected to the control circuit 3.

  The drain terminal of the switching element Q7 is electrically connected to the connection end 2c. The source terminal of the switching element Q7 is electrically connected to the drain terminal of the switching element Q8. The gate terminal of the switching element Q7 is electrically connected to the control circuit 3.

  The drain terminal of the switching element Q8 is electrically connected to the connection end 2b. The source terminal of the switching element Q8 is electrically connected to the connection end 2d. The gate terminal of the switching element Q8 is electrically connected to the control circuit 3.

  The switching circuit 2 is not limited to a full bridge circuit, and may be, for example, a half bridge circuit or a push-pull circuit.

  The control circuit 3 is configured to control the switching circuit 1 and the switching circuit 2. The control circuit 3 is, for example, a microcomputer equipped with a program. The control circuit 3 is not limited to a microcomputer, and may be a control IC, for example.

  The control circuit 3 is configured to control the switching circuit 1 with the first control signal. In other words, the control circuit 3 is configured to control the four switching elements Q1 to Q4 separately by the four first control signals.

  The four first control signals are signals for controlling the corresponding four switching elements Q1 to Q4. That is, the control circuit 3 is configured to control the four switching elements Q1 to Q4 in the switching circuit 1 separately. Each of the four first control signals is, for example, a PWM signal.

  Further, the control circuit 3 is configured to control the switching circuit 2 by the second control signal. In other words, the control circuit 3 is configured to control the four switching elements Q5 to Q8 separately by the four second control signals.

  The four second control signals are signals for controlling the corresponding four switching elements Q5 to Q8. That is, the control circuit 3 is configured to control the four switching elements Q5 to Q8 separately in the switching circuit 2. Each of the four second control signals is, for example, a PWM signal.

  In the DC-DC converter 10, the frequency of each of the four first control signals and the frequency of each of the four second control signals are the same frequency. In the DC-DC converter 10, the duty ratios of the four first control signals are the same as the duty ratios of the four second control signals.

  The control circuit 3 is configured to synchronize the operation of the switching circuit 1 and the operation of the switching circuit 2. In other words, the control circuit 3 is configured to synchronize the switching operations of the four switching elements Q1 to Q4 and the switching operations of the four switching elements Q5 to Q8. For example, the control circuit 3 is configured to simultaneously turn on two switching elements Q1, Q4 and two switching elements Q5, Q8.

  By the way, the control circuit 3 changes the phase of the first control signal and the phase of the second control signal so that the phase difference Td (see FIGS. 2 and 3) between the first control signal and the second control signal is variable. And is configured to adjust. Note that the horizontal axis in FIGS. 2 and 3 represents the time axis.

  For example, as shown in FIG. 2, the control circuit 3 switches the phase of the second control signal that controls the switching element Q5 when the first DC voltage Vd1 is converted into the second DC voltage Vd2. Delayed from the phase of the first control signal for controlling the element Q1. Further, as shown in FIG. 2, when the first DC voltage Vd1 is converted to the second DC voltage Vd2, the control circuit 3 controls the switching element Q2 with the phase of the second control signal that controls the switching element Q6. Delay from the phase of the first control signal. Note that Q1 to Q4 in FIG. 2 represent the waveforms of the first control signals input to the switching elements Q1 to Q4, respectively. Q5 to Q8 in FIG. 2 represent the waveforms of the second control signals input to the switching elements Q5 to Q8, respectively.

  In another example, as shown in FIG. 3, when the control circuit 3 converts the second DC voltage Vd2 into the first DC voltage Vd1, a first control signal for controlling the switching element Q1 is shown. The phase is delayed from the phase of the second control signal that controls the switching element Q5. In addition, as shown in FIG. 3, the control circuit 3 controls the switching element Q6 with the phase of the first control signal for controlling the switching element Q2 when the second DC voltage Vd2 is converted into the first DC voltage Vd1. Delay from the phase of the second control signal. In addition, Q1-Q4 in FIG. 3 represents the waveform of the 1st control signal input into switching element Q1-Q4, respectively. Q5 to Q8 in FIG. 3 represent the waveforms of the second control signals input to the switching elements Q5 to Q8, respectively. The relationship between the phase of the first control signal for controlling the switching element Q4 and the phase of the second control signal for controlling the switching element Q8 is such that the phase of the first control signal for controlling the switching element Q1 and the switching element Q5 are controlled. This is the same as the relationship with the phase of the second control signal. Further, the relationship between the phase of the first control signal for controlling the switching element Q3 and the phase of the second control signal for controlling the switching element Q7 is such that the phase of the first control signal for controlling the switching element Q2 and the phase of the switching element Q6 are as follows. This is the same as the relationship with the phase of the second control signal for controlling the.

  Below, regarding the DC-DC converter 10, an operation when converting the first DC voltage Vd1 into the second DC voltage Vd2 will be described with reference to FIG. The case where the storage battery 11 is charged in advance and the storage battery 11 outputs the first DC voltage Vd1 will be described. Vr in FIG. 2 represents the waveform of the resonance voltage generated in the series circuit 4. Ir in FIG. 2 represents the waveform of the resonance current flowing through the series circuit 4. IQ1 to IQ8 in FIG. 2 represent waveforms of currents flowing through the switching elements Q1 to Q8. Ia1 in FIG. 2 represents the waveform of the current output from the switching circuit 1. Ia2 in FIG. 2 represents the waveform of the current input to the switching circuit 2.

  The control circuit 3 controls the switching circuit 1 so that the two switching elements Q1, Q4 and the two switching elements Q2, Q3 are alternately turned on. Thereby, in the DC-DC converter 10, the switching circuit 1 operates as an inverter circuit that converts the first DC voltage Vd1 into the first AC voltage Va1.

  In the DC-DC converter 10, the first AC voltage Va1 from the switching circuit 1 is resonated by the series circuit 4, and the voltage resonated by the series circuit 4 is applied to the first winding N11 of the transformer T1. As a result, in the DC-DC converter 10, the first induced voltage (second AC voltage Va2) is generated in the second winding N12 of the transformer T1 according to the turns ratio of the transformer T1, and the second AC voltage Va2 is converted to the switching circuit. 2 can be input.

  The control circuit 3 delays the phases of the four second control signals from the phases of the four first control signals. The control circuit 3 controls the switching circuit 2 so that the two switching elements Q5 and Q8 and the two switching elements Q6 and Q7 are alternately turned on. As a result, the DC-DC converter 10 can convert the second AC voltage Va2 input to the switching circuit 2 into the second DC voltage Vd2.

  Therefore, in the DC-DC converter 10, after the switching circuit 1 converts the first DC voltage Vd1 into the first AC voltage Va1, the switching circuit 2 can convert the second AC voltage Va2 into the second DC voltage Vd2. It becomes. As a result, the DC-DC converter 10 can convert the first DC voltage Vd1 to the second DC voltage Vd2, and can apply the second DC voltage Vd2 to the electrolytic capacitor that is the DC voltage source 12. It becomes. In short, in the DC-DC converter 10, the storage battery 11 can be discharged.

  In the following, regarding the DC-DC converter 10, an operation when the second DC voltage Vd2 is converted to the first DC voltage Vd1 will be described with reference to FIG. A case will be described in which charges are stored in advance in the electrolytic capacitor, which is the DC voltage source 12, and the DC voltage source 12 outputs the second DC voltage Vd2. Vr in FIG. 3 represents the waveform of the resonance voltage generated in the series circuit 4. Ir in FIG. 3 represents the waveform of the resonance current flowing through the series circuit 4. IQ1 to IQ8 in FIG. 3 represent waveforms of currents flowing through the switching elements Q1 to Q8. In FIG. 3, Ia1 represents the waveform of the current input to the switching circuit 1. In FIG. 3, Ia2 represents the waveform of the current output from the switching circuit 2.

  The control circuit 3 controls the switching circuit 2 so that the two switching elements Q5 and Q8 and the two switching elements Q6 and Q7 are alternately turned on. Thereby, in the DC-DC converter 10, the switching circuit 2 operates as an inverter circuit that converts the second DC voltage Vd2 into the second AC voltage Va2. Therefore, the DC-DC converter 10 can apply the second AC voltage Va2 converted by the switching circuit 2 to the second winding N12 of the transformer T1. As a result, in the DC-DC converter 10, a second induced voltage is generated in the first winding N11 of the transformer T1.

  In the DC-DC converter 10, the second induced voltage generated in the first winding N <b> 11 of the transformer T <b> 1 is resonated by the series circuit 4, and the voltage (first AC voltage Va <b> 1) resonated by the series circuit 4 is supplied to the switching circuit 1. It becomes possible to input.

  The control circuit 3 delays the phases of the four first control signals from the phases of the four second control signals. The control circuit 3 controls the switching circuit 1 so that the two switching elements Q1 and Q4 and the two switching elements Q2 and Q3 are alternately turned on. Thus, the DC-DC converter 10 can convert the first AC voltage Va input to the switching circuit 1 into the first DC voltage Vd1.

  Therefore, in the DC-DC converter 10, after the switching circuit 2 converts the second DC voltage Vd2 into the second AC voltage Va2, the switching circuit 1 can convert the first AC voltage Va1 into the first DC voltage Vd1. It becomes. As a result, the DC-DC converter 10 can convert the second DC voltage Vd2 to the first DC voltage Vd1, and the first DC voltage Vd1 can be applied to the storage battery 11. In short, the DC-DC converter 10 can charge the storage battery 11.

  As described above, in the DC-DC converter 10, when the first DC voltage Vd1 is converted to the second DC voltage Vd2, the control circuit 3 delays the phase of the second control signal from the phase of the first control signal. As a result, in the DC-DC converter 10, the current Ia1 output from the switching circuit 1 can be made larger than the current Ia2 input to the switching circuit 2. Therefore, the DC-DC converter 10 can convert the first DC voltage Vd1 into the second DC voltage Vd2.

  In the DC-DC converter 10, when the second DC voltage Vd2 is converted into the first DC voltage Vd1, the control circuit 3 delays the phase of the first control signal relative to the phase of the second control signal. As a result, in the DC-DC converter 10, the current Ia2 output from the switching circuit 2 can be made larger than the current Ia1 input to the switching circuit 1. Therefore, the DC-DC converter 10 can convert the second DC voltage Vd2 into the first DC voltage Vd1.

  Therefore, the DC-DC converter 10 can perform voltage conversion bidirectionally with a simple configuration without using the step-up circuit in the DC-DC converter of Conventional Example 1 or the chopper circuit of the DC-DC converter of Conventional Example 2. It becomes possible. As a result, the DC-DC converter 10 can improve the conversion efficiency as compared with the DC-DC converter of Conventional Example 1 and the DC-DC converter of Conventional Example 2. Further, in the DC-DC converter 10, since the chopper circuit in the DC-DC converter of the conventional example 2 is not required, the conversion efficiency is improved in the bidirectional voltage conversion as compared with the DC-DC converter of the conventional example 2. Is possible. That is, the DC-DC converter 10 can perform voltage conversion in both directions, and can improve conversion efficiency in bidirectional voltage conversion.

  Further, in the DC-DC converter 10, the control circuit 3 changes the phase of the first control signal and the phase of the second control signal so that the phase difference between the first control signal and the second control signal is variable. Configured to adjust. As a result, the DC-DC converter 10 can appropriately change the magnitude relationship between the first DC voltage Vd1 and the second DC voltage Vd2. Therefore, in the DC-DC converter 10, the turn ratio of the transformer T1 and the voltage conversion ratio for performing bidirectional voltage conversion between the first DC voltage Vd1 and the second DC voltage Vd2 are bidirectional. It is possible to perform voltage conversion.

  However, in the DC-DC converter 10, conversion efficiency when converting the first DC voltage Vd1 into the second DC voltage Vd2 and conversion of the second DC voltage Vd2 into the first DC voltage Vd1 according to the voltage conversion ratio. There is a possibility that a difference from the conversion efficiency of. Hereinafter, for convenience of explanation, the conversion efficiency when converting the first DC voltage Vd1 to the second DC voltage Vd2 is referred to as “first conversion efficiency”, and the second DC voltage Vd2 is converted to the first DC voltage Vd1. The conversion efficiency at this time is referred to as “second conversion efficiency”.

  The inventor of the present application can suppress the difference between the first conversion efficiency and the second conversion efficiency if the turn ratio of the transformer T1 and the voltage conversion ratio are the same in the DC-DC converter 10. I got the knowledge. However, in the DC-DC converter 10, since the voltage value of the first DC voltage Vd1 and the voltage value of the second DC voltage Vd2 vary within a certain range, the turns ratio of the transformer T1 and the voltage conversion ratio are It is difficult to make the same ratio.

  Therefore, the turns ratio of the transformer T1 is smaller than a value obtained by dividing the maximum value of the first DC voltage Vd1 by the minimum value of the second DC voltage Vd2, and the minimum value of the first DC voltage Vd1 is set to the second DC voltage Vd2. It is preferably larger than the value divided by the maximum value of. The turns ratio of the transformer T1 is represented by a value obtained by dividing the number of turns of the first winding N11 by the number of turns of the second winding N12. As a result, in the DC-DC converter 10, even if the voltage value of the first DC voltage Vd1 and the voltage value of the second DC voltage Vd2 vary within a certain range, the first conversion efficiency and the second It is possible to suppress a difference from the conversion efficiency.

  Further, the turn ratio of the transformer T1 is obtained by dividing the voltage between the terminals of the DC voltage source 12 by the average value of the voltage between the terminals of the storage battery 11 during charging and the voltage between the terminals of the storage battery 11 during discharging. It may be a value within a predetermined range. As a result, the DC-DC converter 10 can bidirectionally convert the first DC voltage Vd1 and the second DC voltage Vd2 depending on the turn ratio of the transformer T1. As a result, the DC-DC converter 10 can suppress a difference between the first conversion efficiency and the second conversion efficiency.

  The frequencies of the first control signal and the second control signal are preferably equal to or higher than the resonance frequency of the series circuit 4. For example, the frequency of each of the first control signal and the second control signal satisfies f ≧ fr when the frequency of each of the first control signal and the second control signal is f and the resonance frequency of the series circuit 4 is fr.

  Thereby, in DC-DC converter 10, it becomes possible to suppress hard switching operation of each of four switching elements Q1-Q4 and four switching elements Q5-Q8. Therefore, in the DC-DC converter 10, switching loss can be suppressed. As a result, in the DC-DC converter 10, the conversion efficiency can be further improved as compared with the DC-DC converter of Conventional Example 1 and the DC-DC converter of Conventional Example 2.

  The control circuit 3 preferably increases the frequency of each of the first control signal and the second control signal when the phase difference Td between the first control signal and the second control signal increases. In the DC-DC converter 10, when the phase difference Td between the first control signal and the second control signal increases, the absolute value of the voltage applied to the series circuit 4 increases. As a result, in the DC-DC converter 10, the energy transfer between the inductor L1 and the capacitor C1 is accelerated compared with the case where the phase difference Td between the first control signal and the second control signal is zero. The resonant frequency of the circuit 4 appears to rise.

  Therefore, in the DC-DC converter 10, when the phase difference Td between the first control signal and the second control signal increases, the frequencies of the first control signal and the second control signal are increased. Thereby, in DC-DC converter 10, it becomes possible to suppress hard switching operation of each of four switching elements Q1-Q4 and four switching elements Q5-Q8. Therefore, in the DC-DC converter 10, switching loss can be suppressed. As a result, in the DC-DC converter 10, the conversion efficiency can be further improved as compared with the DC-DC converter of Conventional Example 1 and the DC-DC converter of Conventional Example 2.

  As shown in FIG. 1, the DC-DC converter 10 further includes a detection circuit 5 that detects the phase of the resonance current Ir flowing through the series circuit 4.

  The detection circuit 5 includes a first detection unit 6 and a second detection unit 7.

  The control circuit 3 determines whether the voltage between the pair of connection terminals 1c and 1d or the voltage between the pair of connection terminals 2a and 2b and the phase of the resonance current Ir correspond to the phase of the resonance current Ir flowing through the series circuit 4. The switching frequency of the switching circuit 1 and the switching circuit 2 is controlled so that the phase difference is small. The phase of the resonance current Ir flowing through the series circuit 4 is detected by the first detection unit 6 or the second detection unit 7.

  More specifically, the control circuit 3 performs switching when the phase of the resonance current Ir is advanced with respect to the voltage between the pair of connection terminals 1c and 1d or the voltage between the pair of connection terminals 2a and 2b. The switching frequency of the circuit 1 and the switching circuit 2 is increased. On the other hand, when the phase of the resonance current Ir is delayed with respect to the voltage between the pair of connection terminals 1c and 1d or the voltage between the pair of connection terminals 2a and 2b, the control circuit 3 Reduce the switching frequency of circuit 2. The switching frequency of the switching circuit 1 and the switching circuit 2 is the same frequency.

  Thereby, in the DC-DC converter 10, it becomes possible to minimize the switching loss of the switching circuit 1 or the switching circuit 2. FIG. Therefore, in the DC-DC converter 10, the conversion efficiency can be further improved as compared with the DC-DC converter of the first conventional example and the DC-DC converter of the second conventional example.

  The phase of the voltage between the pair of connection ends that is the target of the phase difference from the resonance current Ir is preferably the phase of the voltage between the pair of connection ends in the switching circuit that functions as a power supply side. For example, it is desirable that the phase of the voltage between the pair of connection ends to be the target is the phase of the voltage between the pair of connection ends 1c and 1d when power conversion is performed from the switching circuit 1 to the switching circuit 2. In addition, the phase of the voltage between the pair of connection ends to be the object is preferably the phase of the voltage between the pair of connection ends 2a and 2b when power conversion is performed from the switching circuit 2 to the switching circuit 1. The switching frequency means a frequency for switching the four switching elements Q1 to Q4 in the switching circuit 1, for example.

  The detection circuit 5 includes both the first detection unit 6 and the second detection unit 7, but may include only one of the first detection unit 6 and the second detection unit 7. The DC-DC converter 10 includes the detection circuit 5, but may not include the detection circuit 5.

  The detection circuit 5 is configured to detect a detection current flowing through the switching circuit 1 (hereinafter referred to as “first detection current”) and a detection current flowing through the switching circuit 2 (hereinafter referred to as “second detection current”). It is preferable. Specifically, the first detection unit 6 is preferably configured to detect a first detection current flowing in the switching circuit 1. The second detection unit 7 is preferably configured to detect a second detection current flowing through the switching circuit 2.

  The control circuit 3 includes a first control signal and a second control signal so that a difference between the first detection current or the second detection current detected by the detection circuit 5 and a set current preset by the operation unit is reduced. It is preferable that the phase difference Td be controlled to be controlled.

  More specifically, the control circuit 3 decreases the absolute value of the phase difference Td when the absolute value of the first detection current or the second detection current detected by the detection circuit 5 is larger than the absolute value of the set current. . On the other hand, the control circuit 3 increases the absolute value of the phase difference Td when the absolute value of the first detection current or the second detection current detected by the detection circuit 5 is smaller than the absolute value of the set current. Thereby, in the DC-DC converter 10, it becomes possible to select the minimum loss operating point according to the set current of the switching circuit 1 or the switching circuit 2. Therefore, in the DC-DC converter 10, the conversion efficiency can be further improved as compared with the DC-DC converter of Conventional Example 1 and the DC-DC converter of Conventional Example 2.

  In this case, the set current is stored in the storage unit 3 a of the microcomputer that is the control circuit 3. The control circuit 3 performs a comparison operation between the set current stored in the storage unit 3a and the first detection current or the second detection current detected by the detection circuit 5, and based on the calculation result, the first control signal and The second control signal is configured to be generated.

  Incidentally, in the DC-DC converter 10, the voltage value of the first DC voltage Vd1 and the voltage value of the second DC voltage Vd2 may fluctuate outside the allowable range. The allowable range is a range in which the first DC voltage Vd1 and the second DC voltage Vd2 are allowed to vary. That is, in the DC-DC converter 10, the voltage ratio between the first DC voltage Vd1 and the second DC voltage Vd2 may deviate from the turns ratio of the transformer T1, and the operation may become unstable.

  In the DC-DC converter 10, the detection circuit 5 is preferably configured to detect the first DC voltage Vd1 and the second DC voltage Vd2. The detection circuit 5 includes a third detection unit 8 and a fourth detection unit 9. The third detection unit 8 is configured to detect the first DC voltage Vd1. The fourth detection unit 9 is configured to detect the second DC voltage Vd2. The third detection unit 8 and the fourth detection unit 9 are electrically connected to the control circuit 3.

  The control circuit 3 is configured to calculate a voltage ratio between the first DC voltage Vd1 and the second DC voltage Vd2 based on the first DC voltage Vd1 and the second DC voltage Vd2 detected by the detection circuit 5. Preferably it is.

  As shown in FIG. 4, the control circuit 3 has a first operation mode and a second operation mode as specific operation modes for performing specific control, which are different from the above-described control (normal control). . The normal control means that the control circuit 3 delays one phase of the first control signal and the second control signal relative to the other phase of the first control signal and the second control signal. This means that the first switching circuit 1 and the second switching circuit 2 are controlled (A1 region in FIG. 4). Hereinafter, for convenience of explanation, an operation mode in which normal control is performed is referred to as “normal operation mode”.

  In the first operation mode, the control circuit 3 controls the first switching circuit 1 and the second switching circuit 2 so as to be in a specified state to be described later. The specified state is a state in which one phase of the first control signal and the second control signal is delayed from the other phase of the first control signal and the second control signal, and when the other is in the ON state. One is in an off state (see FIGS. 5 and 6). FIG. 5 is a timing chart when the first DC voltage Vd1 is converted to the second DC voltage Vd2 with respect to the DC-DC converter 10. FIG. 6 is a timing chart when the second DC voltage Vd2 is converted to the first DC voltage Vd1 with respect to the DC-DC converter 10. The horizontal axis in FIGS. 5 and 6 represents the time axis.

  Referring to FIG. 5, in the first operation mode, the control circuit 3 delays the phase of the second control signal from the phase of the first control signal, and the second control signal is in the second state when the first control signal is in the ON state. The switching circuit 1 and the switching circuit 2 are controlled so that the control signal is turned off.

  In the second operation mode, the control circuit 3 delays the one phase with respect to the other phase, and the first switching circuit 1 and the second duty ratio become smaller than the one duty ratio. The second switching circuit 2 is controlled (see FIGS. 7 and 8). 7 shows a timing chart when the first DC voltage Vd1 is converted into the second DC voltage Vd2 with respect to the DC-DC converter 10. FIG. FIG. 8 is a timing chart when the second DC voltage Vd2 is converted to the first DC voltage Vd1 with respect to the DC-DC converter 10. The horizontal axis in FIGS. 7 and 8 represents the time axis.

  Referring to FIG. 7, in the second operation mode, the control circuit 3 delays the phase of the second control signal from the phase of the first control signal, and the duty ratio of the first control signal is the second control signal. The switching circuit 1 and the switching circuit 2 are controlled so as to be smaller than the duty ratio. The duty ratio of the first control signal is less than 50%.

  Here, when the phase of the second control signal is delayed from the phase of the first control signal, the duty ratio of the first control signal is proportional to the phase difference Td between the first control signal and the second control signal. Is preferred. This will be specifically described below. For example, when the operation mode is changed from the second operation mode (A5 region in FIG. 4) to the first operation mode (A3 region in FIG. 4), the control circuit 3 determines the duty ratio of the first control signal. It is proportional to the phase difference Td, and the duty ratio of the second control signal is several percent (within a range of 0% to 5%). When the control circuit 3 changes the operation mode from, for example, the second operation mode (A5 region in FIG. 4) to the normal operation mode (right region of the A1 region in FIG. 4), the first control signal Is made proportional to the phase difference Td, and the duty ratio of the second control signal is 50%. When the phase of the first control signal is delayed from the phase of the second control signal, the duty ratio of the second control signal is preferably proportional to the phase difference Td. This will be specifically described below. For example, when the operation mode is changed from the second operation mode (A4 area in FIG. 4) to the first operation mode (A2 area in FIG. 4), the control circuit 3 determines the duty ratio of the second control signal. It is proportional to the phase difference Td, and the duty ratio of the first control signal is several percent (within a range of 0% to 5%). Further, when the control circuit 3 changes the operation mode, for example, from the second operation mode (A4 region in FIG. 4) to the normal operation mode (left region of the A1 region in FIG. 4), the second control signal Is made proportional to the phase difference Td, and the duty ratio of the first control signal is 50%.

  Thus, the control circuit 3 can match the waveforms of the first control signal and the second control signal when switching from the second operation mode to the first operation mode. Further, the control circuit 3 can match the waveforms of the first control signal and the second control signal when switching from the second operation mode to the normal operation mode. As a result, in the DC-DC converter 10, it is possible to avoid a sudden change in the output waveform when the operation mode is switched by the control circuit 3, and the operation of the DC-DC converter 10 can be stabilized.

  The storage unit 3a of the control circuit 3 stores a first set voltage ratio Ra1 (see FIG. 4) and a second set voltage ratio Ra2 (see FIG. 4). Each of the first set voltage ratio Ra1 and the second set voltage ratio Ra2 is a voltage ratio for comparison with the voltage ratio. The second set voltage ratio Ra2 is larger than the first set voltage ratio Ra1.

  The control circuit 3 controls the first switching circuit 1 and the second switching circuit 2 in the first operation mode under the first condition described later. The first condition is when the voltage ratio is smaller than the first set voltage ratio Ra1 and when the second DC voltage Vd2 is converted to the first DC voltage Vd1 (during charging) (A2 region in FIG. 4). .

  Further, the control circuit 3 controls the first switching circuit 1 and the second switching circuit 2 in the first operation mode under the second condition described later. The second condition is when the voltage ratio is larger than the second set voltage ratio Ra2 and when the first DC voltage Vd1 is converted to the second DC voltage Vd2 (during discharging) (A3 region in FIG. 4). .

  The control circuit 3 controls the first switching circuit 1 and the second switching circuit 2 in the second operation mode under a third condition described later. The third condition is that when the voltage ratio is smaller than the first set voltage ratio Ra1 and when the first DC voltage Vd1 is converted to the second DC voltage Vd2 (during discharging), the absolute value of the set current described above is used. This is when the value is less than or equal to the predetermined value (A4 region in FIG. 4).

  Further, the control circuit 3 controls the first switching circuit 1 and the second switching circuit 2 in the second operation mode under a fourth condition described later. The fourth condition is when the voltage ratio is larger than the second set voltage ratio Ra2 and when the second DC voltage Vd2 is converted to the first DC voltage Vd1 (during charging), and the absolute value of the set current is This is when it is equal to or less than the predetermined value (A5 region in FIG. 4).

  Therefore, in the DC-DC converter 10, the control circuit 3 is not limited to the normal operation mode, and the first switching circuit 1 and the second switching circuit 2 are operated in one specific operation mode of the first operation mode and the second operation mode. Is configured to control. As a result, the DC-DC converter 10 can stabilize the operation even when the voltage value of the first DC voltage Vd1 and the voltage value of the second DC voltage Vd2 fluctuate outside the allowable range. .

  In addition, when the control circuit 3 controls the 1st switching circuit 1 and the 2nd switching circuit 2 by 2nd operation mode, it is on condition that the absolute value of setting current is below a predetermined value, However, It is not restricted to this condition Absent.

  When the control circuit 3 controls the first switching circuit 1 and the second switching circuit 2 in the second operation mode, the power obtained by the product of one of the first DC voltage Vd1 and the second DC voltage Vd2 and the set current A condition may be set when the absolute value of is less than or equal to the predetermined value. Further, when the control circuit 3 controls the first switching circuit 1 and the second switching circuit 2 in the second operation mode, the absolute value of the phase difference Td between the first control signal and the second control signal is the above value. It is good also as conditions when it is below a predetermined value.

  Further, the control circuit 3 has both the first operation mode and the second operation mode as operation modes, but is not limited to this, and has one of the first operation mode and the second operation mode. It may be.

  In the DC-DC converter 10, a storage battery 11 is electrically connected between a pair of connection ends 1a and 1b, and a DC voltage source 12 is electrically connected between a pair of connection ends 2c and 2d. Not exclusively. In the DC-DC converter 10, a DC voltage source 12 may be electrically connected between a pair of connection ends 1a and 1b, and a storage battery 11 may be electrically connected between a pair of connection ends 2c and 2d.

  As is clear from the above-described embodiment, the DC-DC converter (10) according to the first aspect of the present invention is configured to convert the first DC voltage (Vd1) and the second DC voltage (Vd2) bidirectionally. It is a DC-DC converter that performs conversion. The DC-DC converter (10) includes a first switching circuit (1) including a first switching element (Q1), an inductor (L1), a capacitor (C1), and a transformer (T1). The DC-DC converter (10) includes a second switching circuit (2) including a second switching element (Q5), and a control circuit that controls the first switching circuit (1) and the second switching circuit (2). (3). The first switching circuit (1) is configured to perform bidirectional voltage conversion between the first DC voltage (Vd1) and the first AC voltage (Va1). The second switching circuit (2) is configured to bi-directionally convert the second AC voltage (Va2) and the second DC voltage (Vd2). The transformer (T1) includes a first winding (N11) and a second winding (N12). The first winding (N11) and the second winding (N12) are magnetically coupled. The first winding (N11) is electrically connected between the pair of connection ends (1c, 1d) on the first AC voltage (Va1) side in the first switching circuit (1). The second winding (N12) is electrically connected between the pair of connection ends (2a, 2b) on the second AC voltage (Va2) side in the second switching circuit (2). The series circuit of the inductor (L1) and the capacitor (C1) is electrically connected in series with the first winding (N11) between the pair of connection ends (1c, 1d) in the first switching circuit (1). Yes.

  According to the first aspect, in the DC-DC converter (10), both of the configurations are simple without using the step-up circuit in the DC-DC converter of Conventional Example 1 or the chopper circuit of the DC-DC converter of Conventional Example 2. It is possible to perform voltage conversion in the direction. As a result, in the DC-DC converter (10), the conversion efficiency can be improved as compared with the DC-DC converter of Conventional Example 1 and the DC-DC converter of Conventional Example 2. Further, in the DC-DC converter (10), since the chopper circuit in the DC-DC converter of the conventional example 2 is not required, the conversion efficiency is improved in bidirectional voltage conversion compared to the DC-DC converter of the conventional example 2. It becomes possible to make it. That is, in the DC-DC converter (10), voltage conversion can be performed in both directions, and conversion efficiency can be improved in bidirectional voltage conversion.

  In the DC-DC converter (10) according to the second aspect of the present invention, in the first aspect, the number of windings of the first winding (N11) is divided by the number of windings of the second winding (N12). The turn ratio of the transformer (T1) represented by the value is smaller than a value obtained by dividing the maximum value of the first DC voltage (Vd1) by the minimum value of the second DC voltage (Vd2), and the first DC voltage ( The minimum value of Vd1) is preferably larger than the value obtained by dividing the minimum value of the second DC voltage (Vd2).

  According to the second aspect, in the DC-DC converter (10), the voltage value of the first DC voltage (Vd1) and the voltage value of the second DC voltage (Vd2) vary within a certain range. Even if it exists, it becomes possible to suppress the difference between the first conversion efficiency and the second conversion efficiency.

  In the DC-DC converter (10) according to the third aspect of the present invention, in the first aspect, one of the first DC voltage (Vd1) and the second DC voltage (Vd2) is a terminal of the storage battery (11). An inter-voltage is preferable. The other of the first DC voltage (Vd1) and the second DC voltage (Vd2) is preferably an inter-terminal voltage of the DC voltage source (12). The turn ratio of the transformer (T1) is obtained by dividing the inter-terminal voltage of the DC voltage source (12) by the average value of the inter-terminal voltage during charging in the storage battery (11) and the inter-terminal voltage during discharging in the storage battery (11). It is preferable that the value is within a predetermined range with the obtained value as a reference value.

  According to the third aspect, in the DC-DC converter (10), the difference between the first conversion efficiency and the second conversion efficiency can be suppressed.

  In the DC-DC converter (10) according to the fourth aspect of the present invention, in any one of the first to third aspects, the control circuit (3) includes the first switching element (Q1). It is preferable that the first switching circuit (1) is controlled by a first control signal to be controlled. Moreover, it is preferable that the control circuit (3) is configured to control the second switching circuit 2 by a second control signal for controlling the second switching element (Q5). Each of the first control signal and the second control signal is preferably a PWM signal. It is preferable that the first control signal and the second control signal have the same frequency and the same duty ratio. The control circuit (3) adjusts the phase of the first control signal and the phase of the second control signal so that the phase difference (Td) between the first control signal and the second control signal is variable. It is preferable that it is comprised.

  According to the fourth aspect, the DC-DC converter (10) can bidirectionally convert the first DC voltage (Vd1) and the second DC voltage (Vd2). The DC-DC converter (10) performs bidirectional voltage conversion with a simple configuration without using the booster circuit in the DC-DC converter of Conventional Example 1 or the chopper circuit in the DC-DC converter of Conventional Example 2. It becomes possible. As a result, in the DC-DC converter (10), the conversion efficiency can be improved as compared with the DC-DC converter of Conventional Example 1 and the DC-DC converter of Conventional Example 2. Further, in the DC-DC converter (10), since the chopper circuit in the DC-DC converter of the conventional example 2 is not required, the conversion efficiency is improved in bidirectional voltage conversion compared to the DC-DC converter of the conventional example 2. It becomes possible to make it. That is, in the DC-DC converter (10), voltage conversion can be performed in both directions, and conversion efficiency can be improved in bidirectional voltage conversion.

  In the DC-DC converter (10) of the fifth aspect according to the present invention, in the fourth aspect, the control circuit (3) controls one phase of the first control signal and the second control signal as the first control. It is preferable to be configured to delay the other phase of the signal and the second control signal.

  According to the fifth aspect, the DC-DC converter (10) can bidirectionally convert the first DC voltage (Vd1) and the second DC voltage (Vd2).

  In the DC-DC converter (10) according to the sixth aspect of the present invention, in the fifth aspect, the frequencies of the first control signal and the second control signal are equal to or higher than the resonance frequency of the series circuit (4). Is preferred.

  According to the sixth aspect, in the DC-DC converter (10), it is possible to suppress the hard switching operation of each of the first switching element (Q1) and the second switching element (Q5). Therefore, in the DC-DC converter (10), switching loss can be suppressed. As a result, in the DC-DC converter (10), the conversion efficiency can be further improved as compared with the DC-DC converter of Conventional Example 1 and the DC-DC converter of Conventional Example 2.

  In the DC-DC converter (10) according to the seventh aspect of the present invention, in the fifth aspect or the sixth aspect, the control circuit (3) is arranged between the first control signal and the second control signal. When the phase difference (Td) increases, it is preferable to increase the frequency of each of the first control signal and the second control signal.

  According to the seventh aspect, the DC-DC converter (10) can suppress the switching loss. As a result, in the DC-DC converter (10), the conversion efficiency can be further improved as compared with the DC-DC converter of Conventional Example 1 and the DC-DC converter of Conventional Example 2.

  In the DC-DC converter (10) according to the eighth aspect of the present invention, in any one of the fifth to seventh aspects, the DC-DC converter (10) is connected to the series circuit (4). It is preferable to further include a detection circuit (5) for detecting the phase of the flowing resonance current (Ir). The control circuit (3) is connected between the pair of connection ends (1c, 1d) in the first switching circuit (1) or the second switching circuit according to the phase of the resonance current (Ir) detected by the detection circuit (5). The first switching circuit (1) and the second switching circuit (2) so that the phase difference between the phase of the voltage between the pair of connection ends (2a, 2b) in (2) and the phase of the resonance current (Ir) is small. It is preferable that the switching frequency of 2) is controlled.

  According to the eighth aspect, in the DC-DC converter (10), the conversion efficiency can be further improved as compared with the DC-DC converter of Conventional Example 1 and the DC-DC converter of Conventional Example 2. .

  In the DC-DC converter (10) according to the ninth aspect of the present invention, in the eighth aspect, the detection circuit (5) detects the detection current flowing through the first switching circuit (1) or the second switching circuit (2). It is preferable that it is comprised so that it may detect. The control circuit (3) has a phase difference between the first control signal and the second control signal so that a difference between the detection current detected by the detection circuit (5) and a preset set current is small. It is preferable that it is comprised so that it may control.

  According to the ninth aspect, in the DC-DC converter (10), the conversion efficiency can be further improved as compared with the DC-DC converter of Conventional Example 1 and the DC-DC converter of Conventional Example 2. Become.

  In the DC-DC converter (10) according to the tenth aspect of the present invention, in the ninth aspect, the detection circuit (5) detects the first DC voltage (Vd1) and the second DC voltage (Vd2). It is preferable that it is comprised. The control circuit (3) has a first DC voltage (Vd1) and a second DC voltage (Vd2) based on the first DC voltage (Vd1) and the second DC voltage (Vd2) detected by the detection circuit (5). It is preferable that the voltage ratio is calculated. The control circuit (3) preferably has a specific operation mode for performing specific control. In the specific operation mode, the control circuit (3) delays the phase of the second control signal from the phase of the first control signal, and the second control signal is turned off when the first control signal is on. Thus, the first switching circuit (1) and the second switching circuit (2) are controlled. The storage unit provided in the control circuit (3) preferably stores a first set voltage ratio and a second set voltage ratio that is larger than the first set voltage ratio. When the voltage ratio is smaller than the first set voltage ratio and converted from the second DC voltage (Vd2) to the first DC voltage (Vd1), the control circuit (3) And switching the first DC voltage (Vd1) to the second DC voltage (Vd2) to control the first switching circuit (1) and the second switching circuit (2) according to the specific operation mode. It is preferable.

  According to the tenth aspect, the DC-DC converter (10) operates even when the voltage value of the first DC voltage Vd1 and the voltage value of the second DC voltage Vd2 do not vary within a certain range. Can be stabilized. That is, in the DC-DC converter 10, there is no restriction on the allowable range in which the first DC voltage Vd1 and the second DC voltage Vd2 vary, and the allowable range in which the first DC voltage Vd1 and the second DC voltage Vd2 vary is expanded. It becomes possible to do.

  In the DC-DC converter (10) according to the eleventh aspect of the present invention, in the tenth aspect, the control circuit (3) has a second operation mode different from the first operation mode which is the specific operation mode. It is preferable. In the second operation mode, the control circuit (3) delays the phase of the second control signal from the phase of the first control signal, and the duty ratio of the first control signal is smaller than the duty ratio of the second control signal. Thus, the first switching circuit (1) and the second switching circuit (2) are controlled. In the control circuit (3), the voltage ratio is smaller than the first set voltage ratio and the first DC voltage (Vd1) is converted to the second DC voltage (Vd2), and the voltage ratio is the second set voltage ratio. Larger than the second DC voltage (Vd2) to the first DC voltage (Vd1), and the set current, the first DC voltage (Vd1) and the second DC voltage (Vd2). When the absolute value of either the power obtained by the product of one of the above and the set current or the phase difference (Td) between the first control signal and the second control signal is equal to or less than a predetermined value, It is preferable to control the first switching circuit (1) and the second switching circuit (2).

  According to the eleventh aspect, the DC-DC converter (10) operates even when the voltage value of the first DC voltage Vd1 and the voltage value of the second DC voltage Vd2 do not vary within a certain range. Can be made more stable. Therefore, in the DC-DC converter 10, it is possible to further expand the allowable range in which the first DC voltage Vd1 and the second DC voltage Vd2 vary.

  In the DC-DC converter (10) of the twelfth aspect according to the present invention, in the eleventh aspect, the duty ratio of the first control signal is the phase difference (Td) between the first control signal and the second control signal. ) Is preferable.

  According to the twelfth aspect, in the DC-DC converter (10), when the control circuit (3) switches from the second operation mode to the first operation mode, the waveforms of the first control signal and the second control signal are displayed. It becomes possible to match. Further, the control circuit (3) can match the waveforms of the first control signal and the second control signal when switching from the second operation mode to the normal operation mode. As a result, in the DC-DC converter (10), it is possible to avoid a sudden change in the output waveform when the operation mode is switched by the control circuit (3), and the operation of the DC-DC converter (10) is stabilized. It becomes possible.

  In the DC-DC converter (10) according to the thirteenth aspect of the present invention, in the ninth aspect, the detection circuit (5) detects the first DC voltage (Vd1) and the second DC voltage (Vd2). It is preferable that it is comprised. The control circuit (3) has a first DC voltage (Vd1) and a second DC voltage (Vd2) based on the first DC voltage (Vd1) and the second DC voltage (Vd2) detected by the detection circuit (5). It is preferable that the voltage ratio is calculated. The control circuit (3) preferably has a specific operation mode for performing specific control. In the specific operation mode, the control circuit (3) delays the phase of the first control signal from the phase of the second control signal, and the first control signal is turned off when the second control signal is on. Thus, the first switching circuit (1) and the second switching circuit (2) are controlled. The storage unit provided in the control circuit (3) preferably stores a first set voltage ratio and a second set voltage ratio that is larger than the first set voltage ratio. When the voltage ratio is smaller than the first set voltage ratio and converted from the second DC voltage (Vd2) to the first DC voltage (Vd1), the control circuit (3) And switching the first DC voltage (Vd1) to the second DC voltage (Vd2) to control the first switching circuit (1) and the second switching circuit (2) according to the specific operation mode. It is preferable.

  According to the thirteenth aspect, the DC-DC converter (10) operates even when the voltage value of the first DC voltage Vd1 and the voltage value of the second DC voltage Vd2 do not vary within a certain range. Can be stabilized. That is, in the DC-DC converter 10, there is no restriction on the allowable range in which the first DC voltage Vd1 and the second DC voltage Vd2 vary, and the allowable range in which the first DC voltage Vd1 and the second DC voltage Vd2 vary is expanded. It becomes possible to do.

  In the DC-DC converter (10) according to the fourteenth aspect of the present invention, in the thirteenth aspect, the control circuit (3) has a second operation mode different from the first operation mode which is the specific operation mode. It is preferable. In the second operation mode, the control circuit (3) delays the phase of the first control signal from the phase of the second control signal, and the duty ratio of the second control signal is smaller than the duty ratio of the first control signal. Thus, the first switching circuit (1) and the second switching circuit (2) are controlled. In the control circuit (3), the voltage ratio is smaller than the first set voltage ratio and the first DC voltage (Vd1) is converted to the second DC voltage (Vd2), and the voltage ratio is the second set voltage ratio. Larger than the second DC voltage (Vd2) to the first DC voltage (Vd1), and the set current, the first DC voltage (Vd1) and the second DC voltage (Vd2). When the absolute value of either the power obtained by the product of one of the above and the set current or the phase difference (Td) between the first control signal and the second control signal is equal to or less than a predetermined value, It is preferable to control the first switching circuit (1) and the second switching circuit (2).

  According to the fourteenth aspect, the DC-DC converter (10) operates even when the voltage value of the first DC voltage Vd1 and the voltage value of the second DC voltage Vd2 do not vary within a certain range. Can be made more stable. Therefore, in the DC-DC converter 10, it is possible to further expand the allowable range in which the first DC voltage Vd1 and the second DC voltage Vd2 vary.

  In the DC-DC converter (10) of the fifteenth aspect according to the present invention, in the fourteenth aspect, the duty ratio of the second control signal is the phase difference (Td) between the first control signal and the second control signal. ) Is preferable.

  According to the fifteenth aspect, in the DC-DC converter (10), when the control circuit (3) switches from the second operation mode to the first operation mode, the waveforms of the first control signal and the second control signal are displayed. It becomes possible to match. Further, the control circuit (3) can match the waveforms of the first control signal and the second control signal when switching from the second operation mode to the normal operation mode. As a result, in the DC-DC converter (10), it is possible to avoid a sudden change in the output waveform when the operation mode is switched by the control circuit (3), and the operation of the DC-DC converter (10) is stabilized. It becomes possible.

  While the invention has been described in terms of several preferred embodiments, various modifications and variations can be made by those skilled in the art without departing from the true spirit and scope of the invention, ie, the claims.

Claims (15)

A DC-DC converter that bi-directionally converts a first DC voltage and a second DC voltage,
A first switching circuit having a first switching element, an inductor, a capacitor, a transformer, a second switching circuit having a second switching element, and a control for controlling the first switching circuit and the second switching circuit With circuit,
The first switching circuit is configured to perform bidirectional voltage conversion between the first DC voltage and the first AC voltage,
The second switching circuit is configured to bi-directionally convert a second AC voltage and the second DC voltage,
The transformer includes a first winding and a second winding, and the first winding and the second winding are magnetically coupled,
The first winding is electrically connected between a pair of connection ends on the first AC voltage side in the first switching circuit,
The second winding is electrically connected between a pair of connection ends on the second AC voltage side in the second switching circuit,
The DC-DC converter, wherein a series circuit of the inductor and the capacitor is electrically connected in series with the first winding between the pair of connection ends in the first switching circuit. The turn ratio of the transformer represented by a value obtained by dividing the number of turns of the first winding by the number of turns of the second winding is such that the maximum value of the first DC voltage is the minimum value of the second DC voltage. 2. The DC-DC converter according to claim 1, wherein the DC-DC converter is smaller than a value divided by a value and larger than a value obtained by dividing the minimum value of the first DC voltage by the maximum value of the second DC voltage. One of the first DC voltage and the second DC voltage is a terminal voltage of the storage battery,
The other of the first DC voltage and the second DC voltage is a voltage between terminals of a DC voltage source,
The turns ratio of the transformer represented by a value obtained by dividing the number of turns of the first winding by the number of turns of the second winding is the voltage between the terminals of the DC voltage source when charging the storage battery. 2. The DC-DC converter according to claim 1, wherein the DC-DC converter is a value within a predetermined range with a value obtained by dividing an average value of an inter-terminal voltage and an inter-terminal voltage during discharging in the storage battery as a reference value. The control circuit controls the first switching circuit by a first control signal for controlling the first switching element, and controls the second switching circuit by a second control signal for controlling the second switching element. Configured as
Each of the first control signal and the second control signal is a PWM signal, and the first control signal and the second control signal have the same frequency and the same duty ratio,
The control circuit adjusts the phase of the first control signal and the phase of the second control signal so that the phase difference between the first control signal and the second control signal is variable. The DC-DC converter according to any one of claims 1 to 3, wherein the DC-DC converter is configured. The control circuit is configured to delay one phase of the first control signal and the second control signal from the other phase of the first control signal and the second control signal. 5. The DC-DC converter according to claim 4, wherein The DC-DC converter according to claim 5, wherein the frequency of each of the first control signal and the second control signal is equal to or higher than a resonance frequency of the series circuit. The control circuit increases a frequency of each of the first control signal and the second control signal when a phase difference between the first control signal and the second control signal increases. The DC-DC converter according to claim 5 or 6. A detection circuit for detecting a phase of a resonance current flowing in the series circuit;
The control circuit includes: a phase of the voltage between the pair of connection ends in the first switching circuit or the second switching circuit, and a phase of the resonance current according to the phase of the resonance current detected by the detection circuit. The switching frequency of the first switching circuit and the second switching circuit is controlled so that a phase difference between the first switching circuit and the second switching circuit is reduced. 8. The DC-DC converter described in 1. The detection circuit is configured to detect a detection current flowing in the first switching circuit or the second switching circuit,
The control circuit sets a phase difference between the first control signal and the second control signal so that a difference between the detection current detected by the detection circuit and a preset set current is small. It is comprised so that it may control. The DC-DC converter of Claim 8 characterized by the above-mentioned. The detection circuit is configured to detect the first DC voltage and the second DC voltage;
The control circuit is configured to calculate a voltage ratio between the first DC voltage and the second DC voltage based on the first DC voltage and the second DC voltage detected by the detection circuit;
The control circuit has a specific operation mode for performing specific control,
In the specific operation mode, the control circuit delays the phase of the second control signal from the phase of the first control signal, and the second control signal is turned off when the first control signal is on. Controlling the first switching circuit and the second switching circuit to be in a state;
The storage unit provided in the control circuit stores a first set voltage ratio and a second set voltage ratio that is larger than the first set voltage ratio,
The control circuit is configured such that when the voltage ratio is smaller than the first set voltage ratio and the second DC voltage is converted to the first DC voltage, the voltage ratio is greater than the second set voltage ratio and 10. The DC according to claim 9, wherein the first switching circuit and the second switching circuit are controlled according to the specific operation mode in each of the conversion from the first DC voltage to the second DC voltage. DC converter. The control circuit has a second operation mode different from the first operation mode which is the specific operation mode,
In the second operation mode, the control circuit delays the phase of the second control signal from the phase of the first control signal, and the duty ratio of the first control signal is the duty ratio of the second control signal. Controlling the first switching circuit and the second switching circuit to be smaller than
The control circuit includes a case where the voltage ratio is smaller than the first set voltage ratio and the first DC voltage is converted to the second DC voltage, and the voltage ratio is greater than the second set voltage ratio. Each of the cases where the second DC voltage is converted to the first DC voltage, and the power obtained by the product of the set current, one of the first DC voltage and the second DC voltage, and the set current When the absolute value of any of the phase differences between the first control signal and the second control signal is less than or equal to a predetermined value, the first switching circuit and the second switching circuit are controlled by the second operation mode. The DC-DC converter according to claim 10. The DC-DC converter according to claim 11, wherein a duty ratio of the first control signal is proportional to a phase difference between the first control signal and the second control signal. The detection circuit is configured to detect the first DC voltage and the second DC voltage;
The control circuit is configured to calculate a voltage ratio between the first DC voltage and the second DC voltage based on the first DC voltage and the second DC voltage detected by the detection circuit;
The control circuit has a specific operation mode for performing specific control,
In the specific operation mode, the control circuit delays the phase of the first control signal from the phase of the second control signal, and the first control signal is turned off when the second control signal is in an on state. Controlling the first switching circuit and the second switching circuit to be in a state;
The storage unit provided in the control circuit stores a first set voltage ratio and a second set voltage ratio that is larger than the first set voltage ratio,
The control circuit is configured such that when the voltage ratio is smaller than the first set voltage ratio and the second DC voltage is converted to the first DC voltage, the voltage ratio is greater than the second set voltage ratio and 10. The DC according to claim 9, wherein the first switching circuit and the second switching circuit are controlled according to the specific operation mode in each of the conversion from the first DC voltage to the second DC voltage. DC converter. The control circuit has a second operation mode different from the first operation mode which is the specific operation mode,
In the second operation mode, the control circuit delays the phase of the first control signal from the phase of the second control signal, and the duty ratio of the second control signal is the duty ratio of the first control signal. Controlling the first switching circuit and the second switching circuit to be smaller than
The control circuit includes a case where the voltage ratio is smaller than the first set voltage ratio and the first DC voltage is converted to the second DC voltage, and the voltage ratio is greater than the second set voltage ratio. Each of the cases where the second DC voltage is converted to the first DC voltage, and the power obtained by the product of the set current, one of the first DC voltage and the second DC voltage, and the set current When the absolute value of any of the phase differences between the first control signal and the second control signal is less than or equal to a predetermined value, the first switching circuit and the second switching circuit are controlled by the second operation mode. The DC-DC converter according to claim 13. The DC-DC converter according to claim 14, wherein a duty ratio of the second control signal is proportional to a phase difference between the first control signal and the second control signal.

Images